Telegraph exchange system



Sept. 19, 1939.

F. s. K INKEAD El AL 2,173,335 TELEGRAPH EXCHANGE SYSTEM 3 Sheets-Sheet1 Filed July 30, 1936 ES. KIN/(54D Ml I/EN TORSV J ER Arro RN Sept. 19,1939.

F. s. KINKEAD .ET AL TELEGRAPH EXCHANGE SYSTEM Filed July .50, 1936 SSheets-Sheet 2 m/w wroks:

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3 Sheets-Sheet 3 F. s. K/NKEAD F.J. SINGER BYiIOI M ATTORNEY I PatentedSept. 19, 1939 UNITED STATES PATENT OFFlCE TELEGRAPH EXCHANGE SYSTEMApplication July 30, 1936, Serial No. 93,368

8 Claims.

The present invention relates to central office circuits including abroadcast arrangement, and trunk circuits for teletypewriter switchingsystems of the type adapted to give teletypewriter service tosubscribers through exchanges.

A particular object of the invention is to simplify teletypewriterexchanges and to this end a typical embodiment of the invention includesa repeaterless cord circuit for interconnecting lines.

Another object is to provide arrangements whereby an exchange includingsaid repeaterless cord circuits may connect one or more lines to adistant exchange over a long toll trunk and to this end a typicalembodiment of the invention includes suitable line terminating equipmentand arrangements whereby such trunk may be connected to the exchangehaving the repeaterless cord circuits through a repeater.

A feature of the invention is its ready adaptability to the setting upof a broadcast arrangement. For this purpose the teletypewriteroperators set at the central office may be simultaneously connected to aplurality of subscribers lines.

A further feature consists of a broadcast cord by means of which anyline terminating at the switchboard may be connected to broadcast to anyreasonable number of other lines.

A feature of the broadcast operation is that all the necessaryinterconnection of lines and/or machines may be accomplished by pluggingcords into line jacks and operating appropriate keys in properdirections.

A circuit arrangement embodying the invention is disclosed in theaccompanying drawings in Which:-

Figs. 1 and 2 taken together illustrate two subscribers lines, two cordcircuits adapted to interconnect subscribers lines, a broadcast cord,and necessary keys and operators sets and other equipment; and

Fig. 3 discloses in more diagrammatic form the relationship between aplurality of subscribers lines and cord circuits associated with themduring broadcasting.

Subscriber to subscriber connection The apparatus will now be describedin connection with the operation of setting up a communication circuitbetween two substations or subscribers stations. Let it first be assumedthat the equipment is in idle condition and the subscriber atsubscribers station SA wishes to make a call. The switch or key P5 isoperated which closes the line from battery over the line relay Llthrough the ring side of the line, the sending contacts of thesubscribers printer and the receiving magnet to ground. It will beunderstood that the switch PS may also start the motor of a subscribersteletype machine by connecting it is to a suitable source of power.Relay Ll operates and energizes the line lamp I over an obvious circuit.The operator places the answering plug 2 of a cord circuit into thesubscribers line jack which deen'ergizes relay LI and extinguishes lampI. Relays AD and Cl in the cord operate. A circuit is now closed from-48 V battery, through the winding of relay AB, to the tip of the lineand back over the ring of the line to the inner left make contact ofrelay AD, through the other winding of relay AB, through thecorresponding broadcast cord key BKI, contacts of cord key GK! andinnerrighthand contact of relay AD to +48 V battery on the left-handarmature of relay CD. By operating key OK! to theright the operatorsprinter OPI may be connected to the cord. By operating key CKI to theleft, another operators printer, not shown, may be connected. Theoperator types an inquiry and the subscriber responds by givinginformation of the station desired. Let it be assumed that a subscriberconnected to the jack 2C is the subscriber desired. The operator putscalling plug 3 into the jack 2C. This causes the operation of the relayCB. It will be noted that the relays AB and CB are differential relays.Relay AB remains released since the subscriber circuit SA is closed andthe current flows through both windings in opposite directions. Relay ADremains operated and the transmission circuit between the-operators setCPI and the subscriber station SA remains closed, as previouslydescribed. Relay CB operates from 48 V bat tery, through normally closedinner right-hand contact of relay CD, right-hand winding of relay CB,tip of plug 3, jack 2C to ground on contacts of key PS in the calledstation. The ring circuit is open at key PS in the station. A circuit isclosed to the lamp 1 associated with the CB relay and the operatorreceives an indication that the station is in the normal idle condition.

To ring the called station the operator operates or depresses theleft-hand portion of key BKI repeatedly. Each time the key is depresseda source of ringing voltage will be applied through the contacts of keyBKI, outer normally closed right-hand contacts of relay CD, ring of plug3, Jack 20, ring conductor of the line to the ringer and its associatedcondenser to ground in the station.

When the called subscriber answers by operating key PS, ground isremoved from the tip circuit, the loop is closed and the ringer isshortcircuited. Since no current flows in either Winding of relay CB, itreleases to extinguish the associated lamp and to operate relay CD. Acommunication circuit is now closed beginning 48 V battery, Winding ofrelay AB, over the tip and ring of the line of the subscriber SA asbefore, back through the ringover the left inner make contact of relayAD, winding of relay AB, keys BKI and CKI, right inner make contact ofrelay CD, right-hand Winding of relay CB, tip of the line connected tothe jack 2C, back through the ring of the jack 20, right outer makecontact of relay CD, left-hand winding of relay CB to +48 V battery. Thesubscribers are now connected and may communicate by teletypewriter overthe circuit described.-

Upon finishing communication either subscriber may give a disconnectsignal by operating key PS to ground the tip of the line whereupon thecorresponding relay AB or CB, as the case may be, operates due to thefact that only one winding thereof is energized which closes a circuitthrough the corresponding lamp 1 to call the operators attention. Theoperator may pull down the plug which operation will extinguish thecorresponding lamp 1.

Pouier supply and night, alarm arrangements If desired, a motorgenerator set may be employed as the source of all the positive andnegative 48-volt battery supply indicated in the draw ings. Such a motorgenerator set may be operated by a motor supplied with energy frompublic utility supply means or any other suitable source. The relay Mmaybe connected to control the motor generator set in any acceptablemanner, for example, as disclosed in'the application of Singer PatentNo, 2,170,038, granted Aug. 22 1939. It is desired that the relay M beenergized whenever a subscriber makes a call by closing the key PS orwhenever any cord plug is connected to a line jack. In order to securethis result the relay M is energized whenever the relay L2 is energizedor whenever relay Cl is energized. To this end it may be assumed thatthe two conductors designated are connected together. Whenever a linerelay Ll is energized the motor generator set is started into operation.More over the connection of any answering plug to 'a jack energizes thecircuit from negative battery through the relay Cl, relay NA, lamp 1,make contact relay AB, if AB is energized to ground on the sleeve ofplug 2. If, however, the relay AB is not energized then the path toground will be over the conductor l2 through the winding of relay AD orCD as the case may be to ground upon the sleeve of jack 2 or any otherjack of the oflice. Consequently, the relay M is energized and suppliespositive and negative 48-volt potential to the exchange whenever therelay M or the relay Cl is energized and relay M is energized whenever asubscribers station is in condition to communicate or whenever a cordplug is in any line jack.

Ina similar manner a night alarm relay NA and the relay L2 control anight alarm circuit. For this purpose conductors l3 may be assumed to beconnected together. Whenever relay Ll operates or whenever relay NA isenergized and operates, a ground is supplied to a circuit which extendsfrom battery through the winding of buzzer relay BZ or a relay BZ whichmay control a buzzer through the night alarm key NK to ground. Thisnight alarm is, therefore, effective both for calling and disconnectsignals so that, if desired, the ofiice may be attended at times oflight business by an attendant primarily engaged in other duties.

Broadcasting Provision is made whereby an operator may broadcast fromher machine to several subscribers lines simultaneously or whereby anoperator at one subscribers station may be connected to broadcast toseveral subscribers stations simultaneously. It will be noticed in Fig.2 that the circuit of one operators machine OPI is shown in full, Thereare three leads to this machine from key OK which are designated a, b,0. Three corresponding leads designated a, b, 0, may extend to anotheroperators machine. By throwing key OK to the left or to the right eitherof these operators machines may be connected to the circuit and when soconnected may function in an identical manner. Let it be assumed thatthe operator wishes to broadcast to a plurality of subscribers lines. Aplug of a cord, such as is shown in Fig, 1, is connected to each suchline and the subscriber is rung in the usual manner. As will beexplained hereinafter, the broadcast may be made to either an even orodd number of subscribers. If the number is even, both ends of the cordsutilized for the purpose are connected to subscribers lines. This,however, is not necessary or essential as a single plug of the cord maybe connected to the subscribers line and the other plug of the cord leftidle; Let it be assumed that the No. 1 and No. 2 cords shown in Fig. 1are each connected to two subscribers lines, making-four in all, andthat the operator wishes to broadcast from machine OPI. Keys BKI and BKZare operated to the right and key OK operated to the left. The operatorsmachine OPI is now connected to the operating circuit of a broadcastrelay BR. The circuit may be traced beginningat +48 V battery on key BKIor BK2 through normally closed contacts on the right key OK, through thecontacts on the left key OK, through lead- 0 to operators set OPI backover lead I), over another operated contact on the left key OK, throughthe upper winding of relay BR. andresistance l5 to -48 V battery on theright back contact of sleeve relay BD of the broadcast cord. As will behereinafter more fully explained in connection with Fig. 3, everysubscribers line connected to the broadcast circuit is now brought totwo common points, these common points being'the two conductors l6 andI1, respectively.

- Assume now-that the operator does not wish to broadcast but that someparticular subscriber wishes to broadcast. The lines of the subscribersto whom the broadcast is to be given are connected over the cordcircuits to the common points represented by the conductors l6, I! asbefore described. The broadcasting plug BP of a broadcast cord isconnected to the line of the subscriber about to broadcast. This causesthe sleeve relay BD to be operated over the sleeve of the broadcastingline and prepares the circuit so that the broadcasting subscriber maygive a disconnect signal on the lamp 1 connected to the broadcast cord.Assuming that the subscribers line is closed and that his teletypewritermachine is operating, .a communication path is amazes closed from thetip-of th e line over the-tip of. the plug BP, a. winding of relay BB to+48 V battery on a makecontact of relay BD. From the ringof the plug thecircuit is closed 'through'the left outer make contact of relay BD andthe other winding of relay-BB, the .operating winding of ER, contacts onkey OK +48 V battery on the lower operated contact of any broadcastingkey BKI, B K2, etc. It is to be understood. that as many of these keysare operated as there are cord circuits to be connected to thebroadcasting line.

It will be noticed that the ringing key RC is provided for ringing-overa line of asubscriber to which the broadcast cord has been connected.

Reference -to Fig. 3 will elucidate the principle of operation of thebroadcast arrangement. As shown the simplified diagram of the circuit isas arranged for broadcasting from. an operators machine. The circuitfrom the operators machine is traced from +48 V battery through thecontacts of BKI BK2 and OK keys diagrammatically indicated, sendingcontacts of operators set OPI, and a contact of key OK diagrammaticallyindicated, the broadcast relay BR, contact of relay BD to 48 V battery.The actuation of the operators machine operates the relay BRaccordingly. The armature of the relay BR transmits the message to alllines which are connected to cord circuits similar to those of Fig. 1with their broadcasting keys BKI, etc. operated. It will be seen thatone-half of the lines, namely those connected to answering plugs 2, have48 V battery connected to the tips, whereas those connected to thecalling plugs have +48 V battery connected to the ring side. Four suchsubscribers stations are shown designated SA, SB, SC and SD. We nowdiscuss what happens in case an odd number of lines is connected toreceive a broadcast and for this purpose let us consider the line of thesubscribers station SD. As set up the circuit extends from +48 V batteryover the sleeve and back through the ring of the line to the commonpoint 11. The sleeve relay CD is operated over its ground on the sleeveof the associated jack. If

now the cord plug connected to the line of subscriber SD is withdrawn,the relay CD releases and upon such release it connects +48 V batterythrough resistance l8 directly to the common point I! in place of the+48 V battery which was previously connected over the resistance of thesubscribers loop to such common point. The battery supply overresistance I8 thus takes the place of the battery supply over thesubscribers line and the resistance l8 replaces the resistance of theline.

On the other hand, if an answering plug is withdrawn from or leftuninserted in a subscribers line, then the relay AD is released and atits right-hand outer break contact connects +48 V battery directlythrough resistance l9 to the common point Hi. In this way any number oflines either even or odd may be connected to receive simultaneously amessage broadcast either from some particular line or from an operatorsmachine at the central office.

Alternative line connections The switchboard circuits so far describedare intended primarily for use in installations having a relativelysmall number of lines, such as exchanges in isolated places and privatebranch exchanges. In order to provide circuits for connecting theswitchboard and its subscribers to a more general teletypewriterexchange system through central oflices, trunk circuits may be provided.Suitable trunk circuits are those illustrat'ed in Figs. 4 and 6 of theapplication of Singer Serial ;No. 89,828, filed July '9, 1936. Eitherend of a double-ended cord, such as those terminated by plugs 2 and 3,may be connected to the line jack of one of those trunk circuits or thebroadcasting-plug B? may be connected thereto. The operation of the cordcircuits will be generally the same as when connected to a subscribersline; the operation of the trunk circuits is set forth in detail in theSinger application.

Furthermore, if one of the subscribers lines is too long for a loopwithout repeaters, it may be connected to the central ofiice by means ofthe circuit including a repeater as shown in Fig. .5 of the aforesaidSinger application.

Service to unattended subscribers station If one or more subscribersshould desire to receive service upon their unattended teletypewriterinstrument, this may be accomplished by utilizing at such subscribersstation the unattended station set shown in Fig. 3 of the aforesaidSinger application. The telephone portion of said unattended station setmay be disregarded or the leads thereto disconnected, retaining only theringer for calling the subscriber from the central office. The operationof said Fig. 3 will be fully understood from the disclosure of the saidSinger application and aside from this will be well understood by thoseskilled in the art, since the telegraph portion of such subscribersequipments are known and in common use.

General comments It will be noted that the cord circuit equipment of thepresent application does not include a telegraph repeater. This is adesirable simplification for many installations where the lines arerelatively short but obviously imposes certain limitations on the use ofthe equipment for interconnecting long subscribers lines. Thebroadcasting arrangement provides an unusually convenient means forestablishing. circuits whereby several subscribers may be interconnectedto receive messages from a single subscriber or from the operator.

What is claimed is:

1. A teletypewriter exchange system comprising a central oflice having acord circuit having two current supply sources of opposite polarity, aplurality of lines extending from said office to subscribers circuits, aplug at each end of said cord circuit for connecting said cord circuitto one of said lines, a key for each cord, connections whereby operationof said key brings such lines as are connected by plugs to said cordcircuits to two common points, and a signal sending device connected tosaid points.

2. A combination according to claim 1, having an operatorsteletypewriter and a key for connecting said operators teletypewriter tooperate said device.

3. In a combination, according to claim 1, a broadcasting cord having aplug for connection to one of said lines, and relays operative to rendersaid line effective to operate said device.

4. In a telegraph exchange system, a plurality of lines, a plurality ofcordcircuits each having two plugs connectible to one of said lines forestablishing through said cord circuit when the two plugs thereof areconnected to two of said lines a two-way telegraphic communication path,

a key for each cord circuit normally isolating the communication pathsof said cord circuits from, each other and contacts upon said keyswhereby operation thereof to a given position brings the communicationpaths of said cord circuits together at two common points. 5. In acombination, according to claim 4, contacts of a broadcasting telegraphimpulse sending device connected across said common points.

6. In a combination, according to claim 4, cperators teletypewriters,and keys individual to said cord circuits for connecting one of saidteletypewriters to the communication path of said cord circuitsindividually.

7. In a teletypewriter exchange system, a broadcast cord connectible toan incoming line by a plug and jack connection, a plurality of othercords, and keys individual to said other cords for connecting them tocommon points controlled by signals from said broadcast cord.

8. In a telegraph exchange system, a plurality of cords terminating inplugs for connection to lines, keys for bringing two points in saidcords to sistance.

FULLERTON S. KINKEAD. FRED J. SINGER.

